Dihydropyrimidines are
prepared by a one-pot cyclo­con­densation of aldehydes, β-ketoesters and urea
in acetonitrile by using bismuth oxide perchlorate as the catalyst for the
first time is described. Compared to the classical Biginelli reaction
conditions, this new method consistently has the advantage of excellent yields
(85-95%) and short reaction time (2-4 hr) at lower temperature (40-50oC).